This invention relates generally to valves and more particularly to gate and other similar type valves having an improved seal member associated with a valving member.
With valves of the type noted above, the valve member seal arrangement includes a groove in a valve body or in a supporting ring structure in which the seal member is often retained by an adhesive. The seal member includes a sealing surface which engages the valve member to form a bubble tight seal. In the construction using an adhesive, the seal member which may be a rubber ring, protrudes from a valve seat surface so that when the valve is closed, there is an interference between the valving member and the rubber ring thereby effecting the bubble-tight seal.
However, there are many problems associated with the adhesively retained seal arrangements. Since the temperature and media limits are not as good as the elastomer used in the seal, premature seal failure results. Also, the flexing of the seal caused by the frictional drag of the valve member upon the seal breaks down the mechanical retention properties of the adhesive until the bond fails. At this point, the seal moves into the pathway of the valve member and is ruined. Improper installation due to the application of too much adhesive or irregularly applied adhesive can cause the seal to fail. In addition, the different set up and cure times of adhesives can cause difficulties. Another problem associated with adhesively retained seals is that of replacing the seals in the field which entails a time consuming and often difficult process of removing the old adhesive from the groove. With respect to valves of the knife gate type, when the adhesive fails, the seal tends to bunch up and be sliced by the knife edge of the gate.
In addition, seals which are retained by means of an adhesive physically confine the seal material along its inner diameter restricting flowability of the seal material. While prior seals have included ribbed portions on the sealing face, the ribbed structure has not permitted sufficient room for the material of the seal to flow when the seal is fully compressed. This restricting of the flowability of the material of the seal causes the seal to be pinched between the knife gate and the valve seat and damaged.